Electromagnetic coil excitation signal modulation device and method

Abstract

The invention relates to an electromagnetic coil excitation signal modulation device and method. A control module outputs a PWM signal of a target frequency to a signal adjustment module, and sends a control voltage corresponding to the target frequency to a voltage-controlled adjustable center frequency point band-pass filter; the signal adjusting module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and a sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled adjustable center frequency point band-pass filter; the voltage-controlled adjustable center frequency point band-pass filter modulates the amplified PWM signal into a same-frequency sine wave signal according to the control voltage sent by the control module and sends the same-frequency sine wave signal to the power amplification module; and the power amplification module performs power amplification on the same-frequency sine wave signal and outputs an excitation signal to the electromagnetic coil. On-line continuous adjustment of a center frequency point is supported, signal modulation is more accurate, and the use reliability in a complex electromagnetic environment is improved.

Description

Technical Field

[0001] The present application relates to the technical field of electromagnetic sensing, and particularly to an electromagnetic coil excitation signal modulation device and method. Background Art

[0002] During the casting process of high-quality continuous casting steel billets, the liquid level height of the molten steel mold is a very important control index. Excessive liquid level fluctuations will not only seriously affect the quality of the steel billets, downgrading their quality, but may also cause forced shutdowns and even safety accidents such as steel leakage, resulting in serious economic losses and personnel risks. Therefore, an electromagnetic sensor is needed to detect the liquid level height. In traditional electromagnetic sensors, the Chinese patent with the publication number CN 216138077U forms a complete detection circuit through a primary coil, a secondary coil, and a cable interface to detect the liquid level of the molten steel mold in real time. However, the excitation signal frequency transmitted to the primary coil in this electromagnetic sensor is fixed and cannot be adjusted online, having the disadvantage of low reliability in use under a complex electromagnetic environment. Summary of the Invention

[0003] Based on this, it is necessary to provide an electromagnetic coil excitation signal modulation device and method that can improve the reliability in use under a complex electromagnetic environment for the above problems.

[0004] The first aspect of the present application provides an electromagnetic coil excitation signal modulation device, including a control module, a signal adjustment module, a voltage-controlled tunable center frequency band-pass filter, a power amplification module, and a feedback sampling module. The control module is connected to the signal adjustment module and the voltage-controlled tunable center frequency band-pass filter. The signal adjustment module is connected to the voltage-controlled tunable center frequency band-pass filter. The power amplification module is connected to the voltage-controlled tunable center frequency band-pass filter and the electromagnetic coil. The feedback sampling module is connected to the power amplification module, the electromagnetic coil, and the signal adjustment module;

[0005] The control module is configured to output a PWM signal with a target frequency to the signal adjustment module, and send a control voltage corresponding to the target frequency to the voltage-controlled tunable center frequency band-pass filter. The signal adjustment module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled tunable center frequency band-pass filter;

[0006] The voltage-controlled adjustable center-frequency bandpass filter modulates the amplified PWM signal into a sine wave signal with the same frequency according to the control voltage sent by the control module and sends it to the power amplification module; the power amplification module amplifies the sine wave signal with the same frequency and outputs an excitation signal to the electromagnetic coil; the feedback sampling module samples the signal of the electromagnetic coil and outputs a sampling signal to the signal conditioning module.

[0007] In one embodiment, the power amplification module is a dual power amplification module. The dual power amplification module amplifies the sine wave signal with the same frequency in phase and in anti-phase respectively, and outputs two excitation signals with a phase difference of 180° and the same amplitude to both ends of the electromagnetic coil respectively.

[0008] In one embodiment, the dual power amplification module includes an operational amplifier inverting proportional amplification unit, an operational amplifier non-inverting proportional amplification unit, a first operational amplifier power amplification unit, and a second operational amplifier power amplification unit. The operational amplifier inverting proportional amplification unit is connected to the voltage-controlled adjustable center-frequency bandpass filter and the first operational amplifier power amplification unit, and the first operational amplifier power amplification unit is connected to the first end of the electromagnetic coil; the operational amplifier non-inverting proportional amplification unit is connected to the voltage-controlled adjustable center-frequency bandpass filter and the second operational amplifier power amplification unit, and the second operational amplifier power amplification unit is connected to the second end of the electromagnetic coil through the feedback sampling module.

[0009] In one embodiment, the signal conditioning module includes an operational amplifier proportional amplification unit, an operational amplifier PI regulator, and a transistor signal amplification unit. The operational amplifier proportional amplification unit is connected to the control module and the operational amplifier PI regulator, the operational amplifier PI regulator is connected to the feedback sampling module and the transistor signal amplification unit, and the transistor signal amplification unit is connected to the control module and the voltage-controlled adjustable center-frequency bandpass filter;

[0010] The operational amplifier proportional amplification unit amplifies the output voltage sent by the control module and outputs an amplified voltage signal to the operational amplifier PI regulator. The operational amplifier PI regulator performs PI feedback regulation according to the amplified voltage signal and the sampling signal output by the feedback sampling module, and outputs a DC voltage to the transistor signal amplification unit. The transistor signal amplification unit outputs an amplified PWM signal with the same frequency as the PWM signal, a high level of the amplitude of the DC voltage, and a low level of 0V to the voltage-controlled adjustable center-frequency bandpass filter.

[0011] In one embodiment, the feedback sampling module is further connected to the control module and outputs a sampling signal to the control module. The control module performs analog-to-digital conversion on the sampling signal to obtain a current value, and sets the output voltage sent to the signal conditioning module according to the current value.

[0012] In one embodiment, the feedback sampling module includes a sampling resistor unit, an operational amplifier differential amplification unit, an operational amplifier band-pass filter, and an operational amplifier full-wave rectification unit. The sampling resistor unit is connected to the power amplification module and the electromagnetic coil. The operational amplifier differential amplification unit is connected to the sampling resistor unit and the operational amplifier band-pass filter. The operational amplifier full-wave rectification unit is connected to the operational amplifier band-pass filter, the signal conditioning module, and the control module.

[0013] In one embodiment, the voltage-controlled adjustable center-frequency band-pass filter includes a frequency-selective filter, a non-linear compensation circuit, and an inverting low-pass filter circuit. The frequency-selective filter is connected to the signal conditioning module, the power amplification module, and the non-linear compensation circuit. The inverting low-pass filter circuit is connected to the non-linear compensation circuit and the control module;

[0014] After amplifying or attenuating the control voltage sent by the control module, the inverting low-pass filter circuit outputs a negative voltage that matches the pinch-off voltage parameter of the field effect transistor in the frequency-selective filter. After compensating the negative voltage, the non-linear compensation circuit conveys it to the frequency-selective filter. The frequency-selective filter adjusts the center frequency using the internal field effect transistor according to the received negative voltage, and modulates the amplified PWM signal into a sine wave signal with the same frequency according to the adjusted center frequency.

[0015] In one embodiment, the frequency-selective filter includes an operational amplifier U1A, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a capacitor C1, a capacitor C2, and a field effect transistor Q1. The control terminal and the first terminal of the field effect transistor Q1 are connected to the non-linear compensation circuit. The second terminal of the field effect transistor Q1 is grounded. The first terminal of the resistor R8 is connected to the first terminal of the field effect transistor Q1 and the first terminal of the resistor R4. The second terminal of the resistor R8 is grounded. The second terminal of the resistor R4 is connected to the first terminal of the resistor R1, the first terminal of the capacitor C1, and the first terminal of the capacitor C2. The second terminal of the resistor R1 is connected to the signal conditioning module. The second terminal of the capacitor C1 is connected to the output terminal of the operational amplifier U1A. The second terminal of the capacitor C2 is connected to the inverting input terminal of the operational amplifier U1A. The non-inverting input terminal of the operational amplifier U1A is grounded through the resistor R5. The first terminal of the resistor R2 is connected to the inverting input terminal of the operational amplifier U1A. The second terminal of the resistor R2 is connected to the output terminal of the operational amplifier U1A. The output terminal of the operational amplifier U1A is connected to the power amplification module.

[0016] In one embodiment, the non-linear compensation circuit includes operational amplifier U1B, operational amplifier U1C, resistor R6, resistor R7, resistor R9, resistor R10, and capacitor C3. The non-inverting input terminal of operational amplifier U1B is connected to the first end of field effect transistor Q1 through resistor R7. The inverting input terminal of operational amplifier U1B is connected to the output terminal of operational amplifier U1B and the first end of resistor R6. The second end of resistor R6 is connected to the control terminal of field effect transistor Q1 and the first end of resistor R9. The second end of resistor R9 is connected to the output terminal of operational amplifier U1C and the inverting input terminal of operational amplifier U1C. The non-inverting input terminal of operational amplifier U1C is connected to the first end of resistor R10 and grounded through capacitor C3. The second end of resistor R10 is connected to the inverting low-pass filter circuit.

[0017] In one embodiment, the inverting low-pass filter circuit includes operational amplifier U1D, resistor R11, resistor R12, resistor R13, and capacitor C4. The non-inverting input terminal of operational amplifier U1D is grounded through resistor R13. The inverting input terminal of operational amplifier U1D is connected to the control module through resistor R12. Resistor R11 and capacitor C4 are connected in parallel, and one end is connected to the inverting input terminal of operational amplifier U1D, and the other end is connected to the output terminal of operational amplifier U1D. The output terminal of operational amplifier U1D is connected to the second end of resistor R10.

[0018] The second aspect of the present application provides an electromagnetic coil excitation signal modulation method, including:

[0019] The control module outputs a PWM signal with a target frequency to the signal conditioning module, and sends a control voltage corresponding to the target frequency to the voltage-controlled tunable center frequency band-pass filter;

[0020] The signal conditioning module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled tunable center frequency band-pass filter; wherein, the feedback sampling module samples the signal of the electromagnetic coil and outputs the sampling signal to the signal conditioning module.

[0021] The voltage-controlled tunable center frequency band-pass filter modulates the amplified PWM signal into a sine wave signal with the same frequency according to the control voltage sent by the control module and sends it to the power amplification module;

[0022] The power amplification module amplifies the sine wave signal with the same frequency and outputs an excitation signal to the electromagnetic coil.

[0023] In the above electromagnetic coil excitation signal modulation device and method, the control module outputs a PWM signal with a target frequency to the signal conditioning module, and sends a control voltage corresponding to the target frequency to the voltage-controlled adjustable center frequency band-pass filter; the signal conditioning module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled adjustable center frequency band-pass filter; the voltage-controlled adjustable center frequency band-pass filter modulates the amplified PWM signal into a sine wave signal with the same frequency according to the control voltage sent by the control module and sends it to the power amplification module; the power amplification module amplifies the sine wave signal with the same frequency and outputs an excitation signal to the electromagnetic coil. The target frequency can be set according to actual needs, and feedback adjustment is performed in combination with the sampling signal output by the feedback sampling module, so that after the voltage-controlled adjustable center frequency band-pass filter outputs a sine wave signal with a corresponding frequency, it is sent to the power amplification module for amplification to obtain the excitation signal of the electromagnetic coil, supporting continuous online adjustment of the center frequency, and the signal modulation is more accurate, improving the reliability of use in a complex electromagnetic environment. Description of the Drawings

[0024] Figure 1 It is a structural block diagram of an electromagnetic coil excitation signal modulation device in an embodiment;

[0025] Figure 2 It is a structural schematic diagram of an electromagnetic coil excitation signal modulation device in an embodiment;

[0026] Figure 3 It is a structural schematic diagram of a voltage-controlled adjustable center frequency band-pass filter in an embodiment;

[0027] Figures 4 to 6 It is a signal analysis schematic diagram of a voltage-controlled adjustable center frequency band-pass filter in Example 1;

[0028] Figures 7 to 9 It is a signal analysis schematic diagram of a voltage-controlled adjustable center frequency band-pass filter in Example 2;

[0029] Figure 10 It is a flowchart of an electromagnetic coil excitation signal modulation method in an embodiment. Detailed Embodiments

[0030] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. It can be understood that in the following embodiments, "connection", if there is a transfer of electrical signals or data between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0032] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / comprising" or "has" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0033] In one embodiment, as Figure 1 shown, there is provided an electromagnetic coil excitation signal modulation device, including a control module 110, a signal conditioning module 120, a voltage-controlled tunable center frequency band-pass filter 130, a power amplification module 140 and a feedback sampling module 150. The control module 110 is connected to the signal conditioning module 120 and the voltage-controlled tunable center frequency band-pass filter 130. The signal conditioning module 120 is connected to the voltage-controlled tunable center frequency band-pass filter 130. The power amplification module 140 is connected to the voltage-controlled tunable center frequency band-pass filter 130 and the electromagnetic coil. The feedback sampling module 150 is connected to the power amplification module 140, the electromagnetic coil and the signal conditioning module 120. The control module 110 is configured to output a PWM (Pulse Width Modulation) signal of a target frequency to the signal conditioning module 120, and send a control voltage corresponding to the target frequency to the voltage-controlled tunable center frequency band-pass filter 130. The signal conditioning module 120 receives the output voltage sent by the control module 110, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module 150, and outputs an amplified PWM signal of the same frequency as the PWM signal to the voltage-controlled tunable center frequency band-pass filter 130. The voltage-controlled tunable center frequency band-pass filter 130 modulates the amplified PWM signal into a sine wave signal of the same frequency according to the control voltage sent by the control module 110 and sends it to the power amplification module 140. The power amplification module 140 amplifies the sine wave signal of the same frequency and outputs an excitation signal to the electromagnetic coil. The feedback sampling module 150 samples the signal of the electromagnetic coil and outputs a sampling signal to the signal conditioning module 120.

[0034] Among them, the electromagnetic coil can be the primary electromagnetic coil of the electromagnetic sensor. An excitation signal is output to the primary electromagnetic coil through the electromagnetic coil excitation signal modulation device, and the electromagnetic sensor then analyzes the induction signal generated by the secondary electromagnetic coil to detect the liquid level height. Among them, the central axis of the primary electromagnetic coil and the central axis of the secondary electromagnetic coil can be perpendicular to each other. For example, the central axis of the primary electromagnetic coil can be arranged parallel to the plane of the liquid level to be detected, and the central axis of the secondary electromagnetic coil can be arranged perpendicular to the plane of the liquid level to be detected, which can make the amplitude of the induced electric field on the secondary electromagnetic coil more sensitive to the change of the liquid level, and the liquid level height detection is more accurate.

[0035] The specific value of the target frequency is not unique and can be set according to actual needs and stored in the control module 110. The control module 110 also stores the amplitudes of the control voltages corresponding to different frequencies. As Figure 2 shown, the control module 110 may specifically include a controller 112, a pulse modulator PWM1, a first digital-to-analog converter DAC1, and a second digital-to-analog converter DAC2. The controller 112 is connected to the pulse modulator PWM1, the first digital-to-analog converter DAC1, and the second digital-to-analog converter DAC2. The controller 112 stores the amplitudes of the control voltages corresponding to different frequencies. The first digital-to-analog converter DAC1 sends an output voltage to the signal conditioning module 120. The controller 112 changes the frequency of the PWM signal output to the signal conditioning module 120 by the pulse modulator PWM1 to the target frequency, and then changes the amplitude of the control voltage output to the voltage-controlled tunable center frequency bandpass filter 130 by the second digital-to-analog converter DAC2, which is the voltage value corresponding to the target frequency pre-stored in the controller 112 for adjusting the center frequency of the voltage-controlled tunable center frequency bandpass filter 130. Specifically, the voltage-controlled tunable center frequency bandpass filter 130 is a frequency selection filter for separating and extracting signals of a specific frequency or signals within a certain spectral "frequency band" from signals of other frequencies. The PWM signal can specifically be a PWM signal with a high level of 3.3V and a low level of 0V. The signal conditioning module 120 performs feedback adjustment based on the received output voltage and the sampling signal sampled by the feedback sampling module 150, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled tunable center frequency bandpass filter 130. The voltage-controlled tunable center frequency bandpass filter 130 modulates the amplified PWM signal into a sine wave signal with the same frequency based on the set center frequency.

[0036] In addition, the electromagnetic coil excitation signal modulation device may further include an operational amplifier inverting proportional amplification circuit 160. The operational amplifier inverting proportional amplification circuit 160 is connected to the control module 110 and the voltage-controlled adjustable center frequency bandpass filter 130, and is specifically connected to the second digital-to-analog converter DAC2 in the control module 110. After inverting and proportionally amplifying the control voltage output by the second digital-to-analog converter DAC2, the operational amplifier inverting proportional amplification circuit 160 delivers it to the voltage-controlled adjustable center frequency bandpass filter 130.

[0037] Further, continuing to refer to Figure 2 , the feedback sampling module 150 is also connected to the control module 110, and outputs a sampling signal to the control module 110. The control module 110 performs analog-to-digital conversion on the sampling signal to obtain a current value, and sets the output voltage sent to the signal conditioning module 120 according to the current value. Among them, the control module 110 may further include an analog-to-digital converter ADC1, and the analog-to-digital converter ADC1 is connected to the feedback sampling module 150 and the controller 112. In this embodiment, the online adjustment of the excitation signal amplitude is realized through the digital current closed-loop control of the controller 112. Using the analog-to-digital converter ADC1 to sample and calibrate to obtain the digital quantity feedback of the current magnitude, the controller 112 specifically can compare the current value converted by the analog-to-digital converter ADC1 with the set current, and adjust the output voltage of the first digital-to-analog converter DAC1 according to the comparison result, so as to realize closed-loop control and digitally set the precise target current value required for the excitation signal online, without adverse effects on the implementation of the subsequent signal processing functions.

[0038] In one embodiment, the signal conditioning module 120 may include an operational amplifier proportional amplification unit 122, an operational amplifier PI regulator 124, and a transistor signal amplification unit 126. The operational amplifier proportional amplification unit 122 is connected to the control module 110 and the operational amplifier PI regulator 124. The operational amplifier PI regulator 124 is connected to the feedback sampling module 150 and the transistor signal amplification unit 126. The transistor signal amplification unit 126 is connected to the control module 110 and the voltage-controlled adjustable center frequency bandpass filter 130. The operational amplifier proportional amplification unit 122 amplifies the output voltage sent by the control module 110 and outputs an amplified voltage signal to the operational amplifier PI regulator 124. The operational amplifier PI regulator 124 performs PI (proportional integral) feedback regulation according to the amplified voltage signal and the sampling signal output by the feedback sampling module 150, and outputs a DC voltage to the transistor signal amplification unit 126. The transistor signal amplification unit 126 outputs an amplified PWM signal with the same frequency as the PWM signal, a high level of the amplitude of the DC voltage, and a low level of 0V to the voltage-controlled adjustable center frequency bandpass filter 130.

[0039] Specifically, the operational amplifier proportional amplification unit 122 is connected to the first digital-to-analog converter DAC1 in the control module 110 and receives the output voltage sent by the first digital-to-analog converter DAC1. The operational amplifier proportional amplification unit 122 can be an inverting operational amplifier proportional amplification unit for voltage amplification. The operational amplifier PI regulator 124 receives the amplified voltage signal output by the operational amplifier proportional amplification unit 122 and performs PI regulation with the sampling signal output by the feedback sampling module 150 to obtain a DC voltage for determining the high-level amplitude of the amplified PWM signal. The transistor signal amplification unit 126 is connected to the pulse modulator PWM1 in the control module 110, and amplifies the received PWM signal with a high level of 3.3V and a low level of 0V into a frequency-preserving amplified PWM signal with a high level of the amplitude of the DC voltage output by the operational amplifier PI regulator 124 and a low level still of 0V. Subsequently, it is modulated into a frequency-preserving sine wave signal by the voltage-controlled tunable center-frequency bandpass filter 130 and sent to the power amplification module 140.

[0040] The power amplification module 140 can be a single power amplification module or a dual power amplification module. In this embodiment, the power amplification module is a dual power amplification module. The dual power amplification module performs in-phase and anti-phase power amplifications according to the frequency-preserving sine wave signal and outputs two excitation signals with a phase difference of 180° and the same amplitude to the two ends of the electromagnetic coil respectively. Specifically, after passing through the voltage-controlled tunable center-frequency bandpass filter 130, the amplified PWM signal obtains a continuous frequency-preserving sine wave signal. After the in-phase power amplification and anti-phase power amplification of this frequency-preserving sine wave signal respectively, two excitation signals with a phase difference of 180° and the same amplitude are simultaneously output to the two connection terminals of the electromagnetic coil. After this modulation, the amplitude of the sine excitation signal finally output to the electromagnetic coil can be doubled compared with the single power amplification scheme, thereby effectively expanding the design boundary of the electromagnetic sensor coil.

[0041] Such as Figure 2As shown, the dual-power amplification module may include an operational amplifier inverting proportional amplification unit 142, an operational amplifier non-inverting proportional amplification unit 144, a first operational amplifier power amplification unit 146, and a second operational amplifier power amplification unit 148. The operational amplifier inverting proportional amplification unit 142 is connected to the voltage-controlled adjustable center frequency bandpass filter 130 and the first operational amplifier power amplification unit 146, and the first operational amplifier power amplification unit 146 is connected to the first end of the electromagnetic coil; the operational amplifier non-inverting proportional amplification unit 144 is connected to the voltage-controlled adjustable center frequency bandpass filter 130 and the second operational amplifier power amplification unit 148, and the second operational amplifier power amplification unit 148 is connected to the second end of the electromagnetic coil through the feedback sampling module 150. After the sine wave signal is amplified by inverting proportional amplification and non-inverting proportional amplification respectively, it is then power-amplified by the first operational amplifier power amplification unit 146 and the second operational amplifier power amplification unit 148 respectively, and two excitation signals with a phase difference of 180° and the same amplitude are output to the two connection terminals of the electromagnetic coil. The total power consumption generated by the power amplification is evenly divided by the two power amplification units, and the possibility of overheating of the device under the same power consumption is smaller, which can enhance the reliability of the system.

[0042] In one embodiment, with continued reference to Figure 2 , the feedback sampling module 150 includes a sampling resistor unit 152, an operational amplifier differential amplification unit 154, an operational amplifier bandpass filter 156, and an operational amplifier full-wave rectification unit 158. The sampling resistor unit 152 is connected to the power amplification module 140 and the electromagnetic coil. The operational amplifier differential amplification unit 154 is connected to the sampling resistor unit 152 and the operational amplifier bandpass filter 156. The operational amplifier full-wave rectification unit 158 is connected to the operational amplifier bandpass filter 156, the signal conditioning module 120, and the control module 110. Among them, the sampling resistor unit 152 is connected between the second operational amplifier power amplification unit 148 and the electromagnetic coil, and the operational amplifier full-wave rectification unit 158 is connected to the operational amplifier PI regulator 124 and the analog-to-digital converter ADC1. The sampling resistor unit 152 generates an induced signal according to the excitation signal flowing through the electromagnetic coil. The induced signal is amplified by the operational amplifier differential amplification unit 154, filtered by the operational amplifier bandpass filter 156, and rectified by the operational amplifier full-wave rectification unit 158, and then a sampling signal is output to the operational amplifier PI regulator 124 and the analog-to-digital converter ADC1. The controller 112 adjusts the output voltage of the first digital-to-analog converter DAC1 according to the current value converted by the analog-to-digital converter ADC1. The operational amplifier PI regulator 124 receives the amplified voltage signal output by the operational amplifier proportional amplification unit 122, and performs PI feedback regulation in combination with the sampling signal output by the operational amplifier full-wave rectification unit 158, and outputs a DC voltage to the transistor signal amplification unit 126. The transistor signal amplification unit 126 amplifies the PWM signal output by the pulse modulator PWM1 into a PWM signal with the same frequency as the high level being the amplitude of the DC voltage output by the operational amplifier PI regulator 124 and the low level being 0V, and sends it to the voltage-controlled adjustable center frequency bandpass filter 130 for signal modulation.

[0043] Furthermore, the specific structure of the voltage-controlled adjustable center frequency bandpass filter 130 is not unique. In one embodiment, as Figure 3 shown, the voltage-controlled adjustable center frequency bandpass filter 130 includes a frequency selection filter 132, a non-linear compensation circuit 134, and an inverting low-pass filter circuit 136. The frequency selection filter 132 is connected to the signal conditioning module 120, the power amplification module 140, and the non-linear compensation circuit 134. The inverting low-pass filter circuit 136 is connected to the non-linear compensation circuit 134 and the control module 110. After amplifying or attenuating the control voltage sent by the control module 110, the inverting low-pass filter circuit 136 outputs a negative voltage that matches the pinch-off voltage parameter of the field effect transistor in the frequency selection filter 132. The non-linear compensation circuit 134 compensates the negative voltage and then sends it to the frequency selection filter 132. The frequency selection filter 132 adjusts the center frequency using the internal field effect transistor according to the received negative voltage, and modulates the amplified PWM signal into a sine wave signal with the same frequency according to the adjusted center frequency.

[0044] Among them, the inverting low-pass filter circuit 136 can be directly (or indirectly) connected to the second digital-to-analog converter DAC2 in the control module 110 to receive the control voltage output by the second digital-to-analog converter DAC2. The frequency selection filter 132 is connected to the transistor signal amplification unit 126, the operational amplifier inverting proportional amplification unit 142, and the operational amplifier non-inverting proportional amplification unit 144, receives the amplified PWM signal VI output by the transistor signal amplification unit 126, and outputs a sine wave signal VO with the same frequency to the operational amplifier inverting proportional amplification unit 142 and the operational amplifier non-inverting proportional amplification unit 144.

[0045] In one embodiment, the frequency selective filter 132 includes an operational amplifier U1A, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a capacitor C1, a capacitor C2, and a field effect transistor Q1. The control terminal and the first terminal of the field effect transistor Q1 are connected to the nonlinear compensation circuit 134. The second terminal of the field effect transistor Q1 is grounded. The first terminal of the resistor R8 is connected to the first terminal of the field effect transistor Q1 and the first terminal of the resistor R4. The second terminal of the resistor R8 is grounded. The second terminal of the resistor R4 is connected to the first terminal of the resistor R1, the first terminal of the capacitor C1, and the first terminal of the capacitor C2. The second terminal of the resistor R1 is connected to the signal conditioning module 120, specifically to the transistor signal amplification unit 126. The second terminal of the capacitor C1 is connected to the output terminal of the operational amplifier U1A. The second terminal of the capacitor C2 is connected to the inverting input terminal of the operational amplifier U1A. The non-inverting input terminal of the operational amplifier U1A is grounded through the resistor R5. The first terminal of the resistor R2 is connected to the inverting input terminal of the operational amplifier U1A. The second terminal of the resistor R2 is connected to the output terminal of the operational amplifier U1A. The output terminal of the operational amplifier U1A is connected to the power amplification module 130. Among them, the field effect transistor Q1 can specifically be a JFET-N transistor, with the gate as the control terminal, the drain as the first terminal, and the source as the second terminal. The frequency selective filter 132 may further include a resistor R3. The output terminal of the operational amplifier U1A is connected to the power amplification module 130 through the resistor R3, specifically connected to the inverting proportional amplification unit 142 and the non-inverting proportional amplification unit 144 of the operational amplifier.

[0046] In the frequency selective filter 132, the resistors R1 and R2 mainly determine the filter gain. The capacitors C1 and C2 can be set to have the same capacitance value. The resistor R2, together with the equivalent resistance formed by the series-parallel connection of the resistors R4, R8, and the field effect transistor Q1, determines the center frequency of the frequency selective filter. The resistor R3 is an output current limiting resistor. Since the field effect transistor Q1 is a JFET transistor, it has a large noise and a larger temperature drift than resistors. Therefore, the resistor R8 is connected in parallel with it, so as to achieve the benefits of reducing noise and temperature drift at the cost of reducing the variable resistance range of the equivalent resistance. The resistor R4 is generally set to be more than twice the maximum value of the equivalent resistance of the parallel connection of the field effect transistor Q1 and the resistor R8. This makes the proportion of the influence of the resistor R4 in the equivalent resistance formed by the resistor R4, the field effect transistor Q1, and the resistor R8 dominant. This is also to further reduce the influence of noise and temperature drift brought by the JFET transistor. In some applications where a very large range of center frequency adjustment is not required, through this design, the circuit can reach a practical range.

[0047] When the parameters of capacitor C1, capacitor C2, resistor R1, and resistor R2 are fixed, the equivalent resistance formed by the series and parallel connection of resistor R4, resistor R8, and field-effect transistor Q1 determines the center frequency of the frequency selection filter 132. When the control voltage VC is 0V, the field-effect transistor Q1 is equivalent to a small resistor. The on-resistance of the field-effect transistor Q1 is connected in parallel with resistor R8 and then in series with resistor R4 to obtain an equivalent resistance. This equivalent resistance, together with capacitor C1, capacitor C2, and resistor R2, determines the initial center frequency of the frequency selection filter 132. When the control voltage VC gradually increases, due to the pinch-off effect of the JFET, the equivalent resistance of the field-effect transistor Q1 gradually increases, resulting in the gradual increase of the equivalent resistance formed by the field-effect transistor Q1, resistor R4, and resistor R8. The center frequency of the frequency selection filter 132 gradually decreases. When the control voltage VC increases to the point where the field-effect transistor Q1 operates in the fully pinched-off region, the center frequency of the frequency selection filter 132 reaches the minimum.

[0048] Further, the non-linear compensation circuit 134 includes operational amplifier U1B, operational amplifier U1C, resistor R6, resistor R7, resistor R9, resistor R10, and capacitor C3. The non-inverting input terminal of operational amplifier U1B is connected to the first terminal of field-effect transistor Q1 through resistor R7. The inverting input terminal of operational amplifier U1B is connected to the output terminal of operational amplifier U1B and the first terminal of resistor R6. The second terminal of resistor R6 is connected to the control terminal of field-effect transistor Q1 and the first terminal of resistor R9. The second terminal of resistor R9 is connected to the output terminal of operational amplifier U1C and the inverting input terminal of operational amplifier U1C. The non-inverting input terminal of operational amplifier U1C is connected to the first terminal of resistor R10 and grounded through capacitor C3. The second terminal of resistor R10 is connected to the inverting low-pass filter circuit 136.

[0049] In addition, the inverting low-pass filter circuit 136 may specifically include operational amplifier U1D, resistor R11, resistor R12, resistor R13, and capacitor C4. The non-inverting input terminal of operational amplifier U1D is grounded through resistor R13. The inverting input terminal of operational amplifier U1D is connected to the control module through resistor R12, specifically connected to the second digital-to-analog converter DAC2 in the control module 110. Resistor R11 and capacitor C4 are connected in parallel, with one end connected to the inverting input terminal of operational amplifier U1D and the other end connected to the output terminal of operational amplifier U1D. The output terminal of operational amplifier U1D is connected to the second terminal of resistor R10.

[0050] The control voltage VC output by the second digital-to-analog converter DAC2 in the control module 110 is generally a positive voltage from zero to several volts. After this positive voltage is amplified or attenuated by a certain ratio through the inverting low-pass filter circuit 132 composed of the operational amplifier U1D, resistors R11, R12, R13, and capacitor C4, a negative voltage matching the pinch-off voltage parameter of the selected JFET transistor is output. This negative voltage can compensate for the non-linearity of the JFET variable resistor through the non-linear compensation circuit 134 composed of the operational amplifier U1B, operational amplifier U1C, and their matching resistors.

[0051] Figures 4 to 6 Schematic diagram for signal analysis of the voltage-controlled adjustable center-frequency band-pass filter 130 in Example 1. As Figure 4 shown, the comparison of the input and output signals of the voltage-controlled adjustable center-frequency band-pass filter 130 that modulates the amplified PWM signal into a sine wave signal of the same frequency. The red one is the PWM signal with an input duty cycle of 50% and a frequency set to 820 Hz, and the blue one is the sine wave signal modulated and output by the voltage-controlled adjustable center-frequency band-pass filter 130. Figure 5 Amplitude-frequency response diagram of the voltage-controlled adjustable center-frequency band-pass filter 130 with the center frequency set to around 820 Hz. Figure 6 Phase-frequency response diagram of the voltage-controlled adjustable center-frequency band-pass filter with the center frequency set to around 820 Hz.

[0052] Figures 7 to 9 Schematic diagram for signal analysis of the voltage-controlled adjustable center-frequency band-pass filter 130 in Example 2. As Figure 7 shown, the comparison of the input and output signals of the voltage-controlled adjustable center-frequency band-pass filter 130 that modulates the amplified PWM signal into a sine wave signal of the same frequency. The red one is the PWM signal with an input duty cycle of 50% and a frequency set to 916 Hz, and the blue one is the sine wave signal modulated and output by the voltage-controlled adjustable center-frequency band-pass filter 130. Figure 8 Amplitude-frequency response diagram of the voltage-controlled adjustable center-frequency band-pass filter 130 with the center frequency set to around 916 Hz. Figure 9 Phase-frequency response diagram of the voltage-controlled adjustable center-frequency band-pass filter with the center frequency set to around 916 Hz.

[0053] The electromagnetic coil excitation signal modulation device provided by this application has a center frequency of the band-pass filter that can be continuously adjusted online by setting the control voltage. Using the current closed-loop control of the controller, the target current value required for the excitation signal can be digitally set online, and the primary coil excitation signal of the electromagnetic sensor can be precisely and digitally set for the frequency and current online. It adopts two power amplification modules to drive together, and the maximum output power of the excitation signal to the electromagnetic coil can be greater, so that a larger effective signal can be obtained on the induction coil of the electromagnetic sensor, and finally the signal-to-noise ratio of the electromagnetic sensing device can be improved. On the other hand, since the amplitude range of the output excitation signal is twice that of the single power amplification scheme, when using this device for signal modulation, there are more optional coil materials and turns when designing the electromagnetic sensor.

[0054] In one embodiment, as Figure 10 shown, there is also provided a method for modulating an electromagnetic coil excitation signal, including:

[0055] Step S110: The control module outputs a PWM signal with a target frequency to the signal adjustment module, and sends a control voltage corresponding to the target frequency to the voltage-controlled adjustable center frequency band-pass filter.

[0056] Step S120: The signal adjustment module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled adjustable center frequency band-pass filter; wherein, the feedback sampling module samples the signal of the electromagnetic coil and outputs the sampling signal to the signal adjustment module.

[0057] Step S130: The voltage-controlled adjustable center frequency band-pass filter modulates the amplified PWM signal into a sine wave signal with the same frequency according to the control voltage sent by the control module and sends it to the power amplification module.

[0058] Step S140: The power amplification module amplifies the sine wave signal with the same frequency and outputs an excitation signal to the electromagnetic coil.

[0059] It can be understood that the specific embodiments of the above method for modulating an electromagnetic coil excitation signal are explained in detail in the above electromagnetic coil excitation signal modulation device, and will not be repeated here.

[0060] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0061] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An electromagnetic coil excitation signal modulation device, characterized in that: It includes a control module, a signal adjustment module, a voltage-controlled adjustable center frequency band-pass filter, a power amplification module and a feedback sampling module, wherein the control module is connected to the signal adjustment module and the voltage-controlled adjustable center frequency band-pass filter, the signal adjustment module is connected to the voltage-controlled adjustable center frequency band-pass filter, the power amplification module is connected to the voltage-controlled adjustable center frequency band-pass filter and the electromagnetic coil, and the feedback sampling module is connected to the power amplification module, the electromagnetic coil and the signal adjustment module; The control module is used to output a PWM signal of a target frequency to the signal adjustment module, and send a control voltage corresponding to the target frequency to the voltage-controlled adjustable center frequency band-pass filter; the signal adjustment module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs an amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled adjustable center frequency band-pass filter; The voltage-controlled adjustable center frequency bandpass filter modulates the amplified PWM signal into a sinusoidal wave signal of the same frequency according to the control voltage sent by the control module and sends it to the power amplifier module; the power amplifier module amplifies the power of the sinusoidal wave signal of the same frequency and outputs an excitation signal to the electromagnetic coil; the feedback sampling module samples the signal of the electromagnetic coil and outputs the sampling signal to the signal adjustment module.

2. The device according to claim 1, characterized in that The power amplification module is a dual power amplification module, which performs in-phase and anti-phase power amplification according to the same-frequency sine wave signal, and outputs two excitation signals with the same amplitude and a phase difference of 180°, which are sent to the two ends of the electromagnetic coil respectively.

3. The device according to claim 2, characterized in that The dual power amplification module includes an operational amplifier inverting proportional amplification unit, an operational amplifier in-phase proportional amplification unit, a first operational amplifier power amplification unit and a second operational amplifier power amplification unit. The operational amplifier inverting proportional amplification unit is connected to the voltage-controlled adjustable center frequency band-pass filter and the first operational amplifier power amplification unit, and the first operational amplifier power amplification unit is connected to the first end of the electromagnetic coil; the operational amplifier in-phase proportional amplification unit is connected to the voltage-controlled adjustable center frequency band-pass filter and the second operational amplifier power amplification unit, and the second operational amplifier power amplification unit is connected to the second end of the electromagnetic coil through the feedback sampling module.

4. The device according to claim 1, characterized in that The signal adjustment module includes an operational amplifier proportional amplification unit, an operational amplifier PI regulator and a transistor signal amplification unit, wherein the operational amplifier proportional amplification unit is connected to the control module and the operational amplifier PI regulator, the operational amplifier PI regulator is connected to the feedback sampling module and the transistor signal amplification unit, and the transistor signal amplification unit is connected to the control module and the voltage-controlled adjustable center frequency bandpass filter; The operational amplifier proportional amplification unit amplifies the output voltage sent by the control module, and outputs the amplified voltage signal to the operational amplifier PI regulator. The operational amplifier PI regulator performs PI feedback regulation according to the amplified voltage signal and the sampling signal output by the feedback sampling module, and outputs a DC voltage to the transistor signal amplification unit. The transistor signal amplification unit outputs the amplified PWM signal with the same frequency as the PWM signal, the high level being the amplitude of the DC voltage, and the low level being 0V to the voltage-controlled adjustable center frequency band-pass filter.

5. The device according to any one of claims 1 to 4, characterized in that: The feedback sampling module is also connected to the control module, and outputs a sampling signal to the control module. The control module performs analog-to-digital conversion on the sampling signal to obtain a current value, and sets an output voltage sent to the signal adjustment module according to the current value.

6. The device according to claim 5, characterized in that The feedback sampling module includes a sampling resistor unit, an operational amplifier differential amplifier unit, an operational amplifier bandpass filter and an operational amplifier full-wave rectifier unit. The sampling resistor unit is connected to the power amplifier module and the electromagnetic coil, the operational amplifier differential amplifier unit is connected to the sampling resistor unit and the operational amplifier bandpass filter, and the operational amplifier full-wave rectifier unit is connected to the operational amplifier bandpass filter, the signal adjustment module and the control module.

7. The device according to any one of claims 1 to 4, characterized in that: The voltage-controlled adjustable center frequency bandpass filter comprises a frequency-selective filter, a nonlinear compensation circuit and an inverting low-pass filter circuit, wherein the frequency-selective filter is connected to the signal adjustment module, the power amplification module and the nonlinear compensation circuit, and the inverting low-pass filter circuit is connected to the nonlinear compensation circuit and the control module; The inverting low-pass filter circuit amplifies or attenuates the control voltage sent by the control module, and outputs a negative voltage that matches the pinch-off voltage parameter of the field effect transistor in the frequency selective filter. The nonlinear compensation circuit compensates the negative voltage and transmits it to the frequency selective filter. The frequency selective filter adjusts the center frequency using the internal field effect transistor according to the received negative voltage, and modulates the amplified PWM signal into a sine wave signal of the same frequency according to the adjusted center frequency.

8. The device according to claim 7, characterized in that The frequency selective filter includes an operational amplifier U1A, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a capacitor C1, a capacitor C2 and a field effect tube Q1. The control end and the first end of the field effect tube Q1 are connected to the nonlinear compensation circuit, the second end of the field effect tube Q1 is grounded, the first end of the resistor R8 is connected to the first end of the field effect tube Q1 and the first end of the resistor R4, the second end of the resistor R8 is grounded, the second end of the resistor R4 is connected to the first end of the resistor R1, the first end of the capacitor C1 and the first end of the capacitor C2, the second end of the resistor R1 is connected to the signal adjustment module, the second end of the capacitor C1 is connected to the output end of the operational amplifier U1A, the second end of the capacitor C2 is connected to the inverting input end of the operational amplifier U1A, the non-inverting input end of the operational amplifier U1A is grounded through the resistor R5, the first end of the resistor R2 is connected to the inverting input end of the operational amplifier U1A, the second end of the resistor R2 is connected to the output end of the operational amplifier U1A, and the output end of the operational amplifier U1A is connected to the power amplifier module.

9. The device according to claim 8, characterized in that The nonlinear compensation circuit includes an operational amplifier U1B, an operational amplifier U1C, a resistor R6, a resistor R7, a resistor R9, a resistor R10 and a capacitor C3. The non-inverting input terminal of the operational amplifier U1B is connected to the first end of the field effect tube Q1 through the resistor R7. The inverting input terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1B and the first end of the resistor R6. The second end of the resistor R6 is connected to the control end of the field effect tube Q1 and the first end of the resistor R9. The second end of the resistor R9 is connected to the output terminal of the operational amplifier U1C and the inverting input terminal of the operational amplifier U1C. The non-inverting input terminal of the operational amplifier U1C is connected to the first end of the resistor R10 and is grounded through the capacitor C3. The second end of the resistor R10 is connected to the inverting low-pass filter circuit.

10. The device according to claim 9, characterized in that The inverting low-pass filter circuit includes an operational amplifier U1D, a resistor R11, a resistor R12, a resistor R13 and a capacitor C4. The non-inverting input terminal of the operational amplifier U1D is grounded through the resistor R13, and the inverting input terminal of the operational amplifier U1D is connected to the control module through the resistor R12. After the resistor R11 and the capacitor C4 are connected in parallel, one end is connected to the inverting input terminal of the operational amplifier U1D, and the other end is connected to the output terminal of the operational amplifier U1D. The output terminal of the operational amplifier U1D is connected to the second end of the resistor R10.

11. A method for modulating an electromagnetic coil excitation signal, characterized in that: include: The control module outputs a PWM signal of a target frequency to the signal conditioning module, and sends a control voltage corresponding to the target frequency to a voltage-controlled adjustable center frequency bandpass filter; The signal adjustment module receives the output voltage sent by the control module, performs feedback adjustment according to the output voltage and the sampling signal output by the feedback sampling module, and outputs the amplified PWM signal with the same frequency as the PWM signal to the voltage-controlled adjustable center frequency bandpass filter; wherein the feedback sampling module performs signal sampling on the electromagnetic coil and outputs the sampling signal to the signal adjustment module; The voltage-controlled adjustable center frequency bandpass filter modulates the amplified PWM signal into a sinusoidal wave signal of the same frequency according to the control voltage sent by the control module and sends it to the power amplifier module; The power amplification module performs power amplification on the same-frequency sine wave signal and outputs an excitation signal to the electromagnetic coil.

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